Building Design and Construction Handbook - Merritt - Ventech!

TABLE 10.8 Size Factors C F for Sawn Lumber
F b
Grades Width, in
WOOD CONSTRUCTION 10.15
Thickness, in
2 and 3 4 F t F c
2, 3, and 4 1.5 1.5 1.5 1.15
Select 5 1.4 1.4 1.4 1.1
Structural, 6 1.3 1.3 1.3 1.1
No. 1 and better, 8 1.2 1.3 1.2 1.05
No. 1, No. 2, 10 1.1 1.2 1.1 1.0
No. 3 12 1.0 1.1 1.0 1.0
14 and wider 0.9 1.0 0.9 0.9
Stud 2, 3 and 4 1.1 1.1 1.1 1.05
5 and 6 1.0 1.0 1.0 1.0
Construction
and Standard
2, 3 and 4 1.0 1.0 1.0 1.0
Utility 4 1.0 1.0 1.0 1.0
2 and 3 0.4 0.4 0.6
10.5.5 Beam Stability Factor
1/9
CF � (12/d) (10.8)
Design values F b for bending should be adjusted by multiplying by the beam stability
factor C L specified in Art. 10.7.2. For glulam beams, the smaller value of C L
and the volume factor C V should be used, not both. See also Art. 10.5.6.
10.5.6 Volume Factor
Design values for bending F b for glulam beams should be adjusted for the effects
of volume by multiplying by
�� �� �� ��
21 12 5.125
CV � K L
(10.9)
L d b
where L � length of beam between inflection points, ft
d � depth, in, of beam
b � width, in, of beam
� width, in, or widest piece in multiple piece layups with various widths
(thus, b � 10.75 in)
x � 20 for southern pine
� 10 for other species
K L � loading condition coefficient (Table 10.9)
For glulam beams, the smaller of C V and the beam stability factor C L should be
used, not both.
1/x